Where was the story arc? SPOILERS
There was no arc, just the two, Helen Mirren and Donald Sutherland, both great actors doing the best they can with the script they were given. But it was just endless episodes, hammered over and over again, illustrating Donald's apparent Alzheimers, his inability to remember anything from their past. Okay we get it already.
Until finally, with about 20 to 25 minutes left of a 1:52 minute movie, there's the reveal that he had carried on an affair years before with the next door neighbor. That did lead to the hilarious scene where Helen, pissed off no end, decides to dump Donald at the nearest retirement facility, and does to the obvious bewilderment and consternation of the staff there. That was probably the best scene of the movie. But the rest was just, over and over, the dilemma of Donald's Alzheimers with no real arc leading anywhere.